Beneath every Google map is a goldmine of data that's hidden from the user; a series of logical statements about places and highways that help provide correct directions, can tell you when traffic's bad, and generally makes the service so much more useful than a paper counterpart.

The Atlantic's Alexis Madrigal was lucky enough to be shown exactly what goes on behind the scenes at Google to make the maps as good as they are. Fortunately he's written about what he saw when he went to visit the guys that work on Google's "Ground Truth":

"Behind every Google Map, there is a much more complex map that's the key to your queries but hidden from your view. The deep map contains the logic of places: their no-left-turns and freeway on-ramps, speed limits and traffic conditions. This is the data that you're drawing from when you ask Google to navigate you from point A to point B...

"Let's step back a tiny bit to recall with wonderment the idea that a single company decided to drive cars with custom cameras over every road they could access. Google is up to five million miles driven now. Each drive generates two kinds of really useful data for mapping. One is the actual tracks the cars have taken; these are proof-positive that certain routes can be taken. The other are all the photos. And what's significant about the photographs in Street View is that Google can run algorithms that extract the traffic signs and can even paste them onto the deep map within their Atlas tool...

"Humans are coding every bit of the logic of the road onto a representation of the world so that computers can simply duplicate (infinitely, instantly) the judgments that a person already made."

He goes on to explain how Google takes raw data from partners, throws in a ton of engineering skill and its own research, and eventually ends up with "something that is higher quality than the sum of its parts." That, however, makes it sound like an automated dream: the flip side is that much of the original data isn't quite perfect and ends up being tweaked by hand. By hand.

All in, the Atlantic piece makes for a fascinating insight into how one of Google's most useful products comes into being. Read it, and you might not take Maps for granted anymore—well, for a minute or two at least. [Atlantic]